Many times(about 50 %), when I add an arrow to a line, the arrow is on the wrong side of the line. So,I have to unselect the arrow on the wrong side and add the arrow on the right one. So having a way to switch (permute) arrows in a line, would be fine
Simple solution out of the box: Create drawing styles for the left arrow and the right arrow (and probably none as well) and apply the style instead of changing the line attributes.